Systems and methods for instillation purging

ABSTRACT

An apparatus for treating a tissue site comprising a negative-pressure source configured to be fluidly coupled to the tissue site; an instillation source configured to be fluidly coupled to the tissue site; and a controller operatively coupled to the negative-pressure source and to the instillation source. The controller can be configured to operate the negative-pressure source and the instillation source to intermittently deliver negative pressure to the tissue site for a negative-pressure interval and deliver instillation fluid to the tissue site for an instillation interval. A purge volume of instillation fluid may be delivered to the tissue site at a purge frequency. In some examples, the purge volume may be delivered through the second fluid conductor and removed through the first fluid conductor during a negative-pressure interval.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 16/747,194, filed Jan. 20, 2020, which claims the benefit, under 35USC § 119(e), of the filing of U.S. Provisional Patent Application No.62/797,035, filed Jan. 25, 2019, which is incorporated herein byreference for all purposes.

TECHNICAL FIELD

The invention set forth in the appended claims relates generally totissue treatment systems and more particularly, but without limitation,to treating tissue with negative-pressure and instillation therapy.

BACKGROUND

Clinical studies and practice have shown that reducing pressure inproximity to a tissue site can augment and accelerate growth of newtissue at the tissue site. The applications of this phenomenon arenumerous, but it has proven particularly advantageous for treatingwounds. Regardless of the etiology of a wound, whether trauma, surgery,or another cause, proper care of the wound is important to the outcome.Treatment of wounds or other tissue with reduced pressure may becommonly referred to as “negative-pressure therapy,” but is also knownby other names, including “negative-pressure wound therapy,”“reduced-pressure therapy,” “vacuum therapy,” “vacuum-assisted closure,”and “topical negative-pressure,” for example. Negative-pressure therapymay provide a number of benefits, including migration of epithelial andsubcutaneous tissues, improved blood flow, and micro-deformation oftissue at a wound site. Together, these benefits can increasedevelopment of granulation tissue and reduce healing times.

There is also widespread acceptance that cleansing a tissue site can behighly beneficial for new tissue growth. For example, a wound or acavity can be washed out with a liquid solution for therapeuticpurposes. These practices are commonly referred to as “irrigation” and“lavage”. “Instillation” is another practice that generally refers to aprocess of slowly introducing fluid to a tissue site and leaving thefluid for a prescribed period of time before removing the fluid. Forexample, instillation of topical treatment solutions over a wound bedcan be combined with negative-pressure therapy to further promote woundhealing by loosening soluble contaminants in a wound bed and removinginfectious material. As a result, soluble bacterial burden can bedecreased, contaminants removed, and the wound cleansed.

While the clinical benefits of negative-pressure therapy and/orinstillation therapy are widely known, improvements to therapy systems,components, and processes may benefit healthcare providers and patients.

BRIEF SUMMARY

New and useful systems, apparatuses, and methods for treating tissuewith negative pressure, instillation of therapeutic solutions, or both,are set forth in the appended claims. Illustrative embodiments are alsoprovided to enable a person skilled in the art to make and use theclaimed subject matter.

For example, in some embodiments, a therapy apparatus may be capable ofintermittently delivering various instillation solutions to a wound bed.Solution instillation can occur during a pause in negative pressure,allowing the solution to soak and solubilize wound debris for a settime. The solution and solubilized debris can be removed during asubsequent cycle of negative pressure. The therapy apparatus mayadditionally have a controller configured to provide intermittent purgecycles of vacuum tubing during a negative-pressure phase to minimizewound fluid build-up and potential blockage. Additionally oralternatively, the controller may be configured to provide intermittentpurge cycles of instillation tubing using a relatively small volume ofinstillation solution to minimize the deposition of material at theinterface between a dressing and tubing. Software controls may provide auser interface for setting various levels of instillation purge. Forexample, the level may depend on the type of instillation solution andother factors associated with the wound etiology, which can impactviscosity and other exudate characteristics.

More generally, an apparatus for treating a tissue site may comprise anegative-pressure source configured to be fluidly coupled to the tissuesite; an instillation source configured to be fluidly coupled to thetissue site; and a controller operatively coupled to thenegative-pressure source and to the instillation source. In someexamples, the negative-pressure source may be coupled to a first fluidconductor configured to be coupled to a dressing, and the instillationsource may be coupled to a second fluid conductor configured to becoupled to the dressing. The controller can be configured to operate thenegative-pressure source and the instillation source to intermittentlydeliver negative pressure to the tissue site for a negative-pressureinterval and deliver instillation fluid to the tissue site for aninstillation interval. A purge volume of instillation fluid may bedelivered to the tissue site at a purge frequency. In some examples, thepurge volume may be delivered through the second fluid conductor andremoved through the first fluid conductor during a negative-pressureinterval.

A method of treating a tissue site with negative-pressure andtherapeutic solution can comprise delivering the negative pressure tothe tissue site for a first interval; delivering the therapeuticsolution to the tissue site for a second interval; and delivering apurge volume of the therapeutic solution to the tissue site during thefirst interval. Alternatively, the purge volume may be delivered beforethe first interval. The purge volume may be removed by negative pressureduring the first interval.

Objectives, advantages, and a preferred mode of making and using theclaimed subject matter may be understood best by reference to theaccompanying drawings in conjunction with the following detaileddescription of illustrative embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram of an example embodiment of atherapy system that can provide negative-pressure treatment andinstillation treatment in accordance with this specification;

FIG. 2 is a graph illustrating additional details of example pressurecontrol modes that may be associated with some embodiments of thetherapy system of FIG. 1 ;

FIG. 3 is a graph illustrating additional details that may be associatedwith another example pressure control mode in some embodiments of thetherapy system of FIG. 1 ;

FIG. 4 is a chart illustrating details that may be associated with anexample method of operating the therapy system of FIG. 1 ; and

FIG. 5 is a graph illustrating additional details of another examplecontrol mode that may be associated with some embodiments of the therapysystem of FIG. 1 .

DESCRIPTION OF EXAMPLE EMBODIMENTS

The following description of example embodiments provides informationthat enables a person skilled in the art to make and use the subjectmatter set forth in the appended claims, but it may omit certain detailsalready well known in the art. The following detailed description is,therefore, to be taken as illustrative and not limiting.

The example embodiments may also be described herein with reference tospatial relationships between various elements or to the spatialorientation of various elements depicted in the attached drawings. Ingeneral, such relationships or orientation assume a frame of referenceconsistent with or relative to a patient in a position to receivetreatment. However, as should be recognized by those skilled in the art,this frame of reference is merely a descriptive expedient rather than astrict prescription.

Therapy System

FIG. 1 is a simplified functional block diagram of an example embodimentof a therapy system 100 that can provide negative-pressure therapy withinstillation of topical treatment solutions to a tissue site inaccordance with this specification.

The term “tissue site” in this context broadly refers to a wound,defect, or other treatment target located on or within tissue,including, but not limited to, bone tissue, adipose tissue, muscletissue, neural tissue, dermal tissue, vascular tissue, connectivetissue, cartilage, tendons, or ligaments. A wound may include chronic,acute, traumatic, subacute, and dehisced wounds, partial-thicknessburns, ulcers (such as diabetic, pressure, or venous insufficiencyulcers), flaps, and grafts, for example. The term “tissue site” may alsorefer to areas of any tissue that are not necessarily wounded ordefective, but are instead areas in which it may be desirable to add orpromote the growth of additional tissue. For example, negative pressuremay be applied to a tissue site to grow additional tissue that may beharvested and transplanted.

The therapy system 100 may include a source or supply of negativepressure, such as a negative-pressure source 105, and one or moredistribution components. A distribution component is preferablydetachable and may be disposable, reusable, or recyclable. A dressing,such as a dressing 110, and a fluid container, such as a container 115,are examples of distribution components that may be associated with someexamples of the therapy system 100. As illustrated in the example ofFIG. 1 , the dressing 110 may comprise or consist essentially of atissue interface 120, a cover 125, or both in some embodiments.

A fluid conductor is another illustrative example of a distributioncomponent. A “fluid conductor,” in this context, broadly includes atube, pipe, hose, conduit, or other structure with one or more lumina oropen pathways adapted to convey a fluid between two ends. Typically, atube is an elongated, cylindrical structure with some flexibility, butthe geometry and rigidity may vary. Moreover, some fluid conductors maybe molded into or otherwise integrally combined with other components.Distribution components may also include or comprise interfaces or fluidports to facilitate coupling and de-coupling other components. In someembodiments, for example, a dressing interface may facilitate coupling afluid conductor to the dressing 110. For example, such a dressinginterface may be a SENSAT.R.A.C.™ Pad, available from Kinetic Concepts,Inc. of San Antonio, Texas.

The therapy system 100 may also include a regulator or controller, suchas a controller 130. Additionally, the therapy system 100 may includesensors to measure operating parameters and provide feedback signals tothe controller 130 indicative of the operating parameters. Asillustrated in FIG. 1 , for example, the therapy system 100 may includea first sensor 135 and a second sensor 140 coupled to the controller130.

The therapy system 100 may also include a source of instillationsolution. In some examples, an instillation source may comprise asolution source operatively coupled to a positive-pressure source. Forexample, a solution source 145 may be fluidly coupled to the dressing110, as illustrated in the example embodiment of FIG. 1 . The solutionsource 145 may be fluidly coupled to a pump or other positive-pressuresource, such as a positive-pressure source 150, a negative-pressuresource, such as the negative-pressure source 105, or both, in someembodiments. A regulator, such as an instillation regulator 155, mayalso be fluidly coupled to the solution source 145 and the dressing 110to ensure proper dosage of instillation solution (e.g. saline) to atissue site. For example, the instillation regulator 155 may comprise apiston that can be pneumatically actuated by the negative-pressuresource 105 to draw instillation solution from the solution source duringa negative-pressure interval and to instill the solution to a dressingduring a venting interval. Additionally or alternatively, the controller130 may be coupled to the negative-pressure source 105, thepositive-pressure source 150, or both, to control dosage of instillationsolution to a tissue site. In some embodiments, the instillationregulator 155 may also be fluidly coupled to the negative-pressuresource 105 through the dressing 110, as illustrated in the example ofFIG. 1 .

Some components of the therapy system 100 may be housed within or usedin conjunction with other components, such as sensors, processing units,alarm indicators, memory, databases, software, display devices, or userinterfaces that further facilitate therapy. For example, in someembodiments, the negative-pressure source 105 may be combined with thecontroller 130, the solution source 145, and other components into atherapy unit.

In general, components of the therapy system 100 may be coupled directlyor indirectly. For example, the negative-pressure source 105 may bedirectly coupled to the container 115 and may be indirectly coupled tothe dressing 110 through the container 115. Coupling may include fluid,mechanical, thermal, electrical, or chemical coupling (such as achemical bond), or some combination of coupling in some contexts. Forexample, the negative-pressure source 105 may be electrically coupled tothe controller 130 and may be fluidly coupled to one or moredistribution components to provide a fluid path to a tissue site. Insome embodiments, components may also be coupled by virtue of physicalproximity, being integral to a single structure, or being formed fromthe same piece of material.

A negative-pressure supply, such as the negative-pressure source 105,may be a reservoir of air at a negative pressure or may be a manual orelectrically-powered device, such as a vacuum pump, a suction pump, awall suction port available at many healthcare facilities, or amicro-pump, for example. “Negative pressure” generally refers to apressure less than a local ambient pressure, such as the ambientpressure in a local environment external to a sealed therapeuticenvironment. In many cases, the local ambient pressure may also be theatmospheric pressure at which a tissue site is located. Alternatively,the pressure may be less than a hydrostatic pressure associated withtissue at the tissue site. Unless otherwise indicated, values ofpressure stated herein are gauge pressures. References to increases innegative pressure typically refer to a decrease in absolute pressure,while decreases in negative pressure typically refer to an increase inabsolute pressure. While the amount and nature of negative pressureprovided by the negative-pressure source 105 may vary according totherapeutic requirements, the pressure is generally a low vacuum, alsocommonly referred to as a rough vacuum, between −5 mm Hg (−667 Pa) and−500 mm Hg (−66.7 kPa). Common therapeutic ranges are between −50 mm Hg(−6.7 kPa) and −300 mm Hg (−39.9 kPa).

The container 115 is representative of a container, canister, pouch, orother storage component, which can be used to manage exudates and otherfluids withdrawn from a tissue site. In many environments, a rigidcontainer may be preferred or required for collecting, storing, anddisposing of fluids. In other environments, fluids may be properlydisposed of without rigid container storage, and a re-usable containercould reduce waste and costs associated with negative-pressure therapy.

A controller, such as the controller 130, may be a microprocessor orcomputer programmed to operate one or more components of the therapysystem 100, such as the negative-pressure source 105. In someembodiments, for example, the controller 130 may be a microcontroller,which generally comprises an integrated circuit containing a processorcore and a memory programmed to directly or indirectly control one ormore operating parameters of the therapy system 100. Operatingparameters may include the power applied to the negative-pressure source105, the pressure generated by the negative-pressure source 105, or thepressure distributed to the tissue interface 120, for example. Thecontroller 130 is also preferably configured to receive one or moreinput signals, such as a feedback signal, and programmed to modify oneor more operating parameters based on the input signals.

Sensors, such as the first sensor 135 and the second sensor 140, aregenerally known in the art as any apparatus operable to detect ormeasure a physical phenomenon or property, and generally provide asignal indicative of the phenomenon or property that is detected ormeasured. For example, the first sensor 135 and the second sensor 140may be configured to measure one or more operating parameters of thetherapy system 100. In some embodiments, the first sensor 135 may be atransducer configured to measure pressure in a pneumatic pathway andconvert the measurement to a signal indicative of the pressure measured.In some embodiments, for example, the first sensor 135 may be apiezo-resistive strain gauge. The second sensor 140 may optionallymeasure operating parameters of the negative-pressure source 105, suchas a voltage or current, in some embodiments. Preferably, the signalsfrom the first sensor 135 and the second sensor 140 are suitable as aninput signal to the controller 130, but some signal conditioning may beappropriate in some embodiments. For example, the signal may need to befiltered or amplified before it can be processed by the controller 130.Typically, the signal is an electrical signal, but may be represented inother forms, such as an optical signal.

The tissue interface 120 can be generally adapted to partially or fullycontact a tissue site. The tissue interface 120 may take many forms, andmay have many sizes, shapes, or thicknesses, depending on a variety offactors, such as the type of treatment being implemented or the natureand size of a tissue site. For example, the size and shape of the tissueinterface 120 may be adapted to the contours of deep and irregularshaped tissue sites. Any or all of the surfaces of the tissue interface120 may have an uneven, coarse, or jagged profile.

In some embodiments, the tissue interface 120 may comprise or consistessentially of a manifold. A manifold in this context may comprise orconsist essentially of a means for collecting or distributing fluidacross the tissue interface 120 under pressure. For example, a manifoldmay be adapted to receive negative pressure from a source and distributenegative pressure through multiple apertures across the tissue interface120, which may have the effect of collecting fluid from across a tissuesite and drawing the fluid toward the source. In some embodiments, thefluid path may be reversed or a secondary fluid path may be provided tofacilitate delivering fluid, such as fluid from a source of instillationsolution, across a tissue site.

In some illustrative embodiments, a manifold may comprise a plurality ofpathways, which can be interconnected to improve distribution orcollection of fluids. In some illustrative embodiments, a manifold maycomprise or consist essentially of a porous material havinginterconnected fluid pathways. Examples of suitable porous material thatcan be adapted to form interconnected fluid pathways (e.g., channels)may include cellular foam, including open-cell foam such as reticulatedfoam; porous tissue collections; and other porous material such as gauzeor felted mat that generally include pores, edges, and/or walls.Liquids, gels, and other foams may also include or be cured to includeapertures and fluid pathways. In some embodiments, a manifold mayadditionally or alternatively comprise projections that forminterconnected fluid pathways. For example, a manifold may be molded toprovide surface projections that define interconnected fluid pathways.

In some embodiments, the tissue interface 120 may comprise or consistessentially of reticulated foam having pore sizes and free volume thatmay vary according to needs of a prescribed therapy. For example,reticulated foam having a free volume of at least 90% may be suitablefor many therapy applications, and foam having an average pore size in arange of 400-600 microns (40-50 pores per inch) may be particularlysuitable for some types of therapy. The tensile strength of the tissueinterface 120 may also vary according to needs of a prescribed therapy.For example, the tensile strength of foam may be increased forinstillation of topical treatment solutions. The 25% compression loaddeflection of the tissue interface 120 may be at least 0.35 pounds persquare inch, and the 65% compression load deflection may be at least0.43 pounds per square inch. In some embodiments, the tensile strengthof the tissue interface 120 may be at least 10 pounds per square inch.The tissue interface 120 may have a tear strength of at least 2.5 poundsper inch. In some embodiments, the tissue interface may be foamcomprised of polyols, such as polyester or polyether, isocyanate, suchas toluene diisocyanate, and polymerization modifiers, such as aminesand tin compounds. In some examples, the tissue interface 120 may bereticulated polyurethane foam such as found in GRANUFOAM™ dressing orV.A.C. VERAFLO™ dressing, both available from Kinetic Concepts, Inc. ofSan Antonio, Texas.

The thickness of the tissue interface 120 may also vary according toneeds of a prescribed therapy. For example, the thickness of the tissueinterface may be decreased to reduce tension on peripheral tissue. Thethickness of the tissue interface 120 can also affect the conformabilityof the tissue interface 120. In some embodiments, a thickness in a rangeof about millimeters to 10 millimeters may be suitable.

The tissue interface 120 may be either hydrophobic or hydrophilic. In anexample in which the tissue interface 120 may be hydrophilic, the tissueinterface 120 may also wick fluid away from a tissue site, whilecontinuing to distribute negative pressure to the tissue site. Thewicking properties of the tissue interface 120 may draw fluid away froma tissue site by capillary flow or other wicking mechanisms. An exampleof a hydrophilic material that may be suitable is a polyvinyl alcohol,open-cell foam such as V.A.C. WHITEFOAM™ dressing available from KineticConcepts, Inc. of San Antonio, Texas. Other hydrophilic foams mayinclude those made from polyether. Other foams that may exhibithydrophilic characteristics include hydrophobic foams that have beentreated or coated to provide hydrophilicity.

In some embodiments, the tissue interface 120 may be constructed frombioresorbable materials. Suitable bioresorbable materials may include,without limitation, a polymeric blend of polylactic acid (PLA) andpolyglycolic acid (PGA). The polymeric blend may also include, withoutlimitation, polycarbonates, polyfumarates, and capralactones. The tissueinterface 120 may further serve as a scaffold for new cell-growth, or ascaffold material may be used in conjunction with the tissue interface120 to promote cell growth. A scaffold is generally a substance orstructure used to enhance or promote the growth of cells or formation oftissue, such as a three-dimensional porous structure that provides atemplate for cell growth. Illustrative examples of scaffold materialsinclude calcium phosphate, collagen, PLA/PGA, coral hydroxy apatites,carbonates, or processed allograft materials.

In some embodiments, the cover 125 may provide a bacterial barrier andprotection from physical trauma. The cover 125 may also be constructedfrom a material that can reduce evaporative losses and provide a fluidseal between two components or two environments, such as between atherapeutic environment and a local external environment. The cover 125may comprise or consist of, for example, an elastomeric film or membranethat can provide a seal adequate to maintain a negative pressure at atissue site for a given negative-pressure source. The cover 125 may havea high moisture-vapor transmission rate (MVTR) in some applications. Forexample, the MVTR may be at least 250 grams per square meter pertwenty-four hours (g/m²/24 hours) in some embodiments, measured using anupright cup technique according to ASTM E96/E96M Upright Cup Method at38° C. and 10% relative humidity (RH). In some embodiments, an MVTR upto 5,000 g/m²/24 hours may provide effective breathability andmechanical properties.

In some example embodiments, the cover 125 may be a polymer drape, suchas a polyurethane film, that is permeable to water vapor but impermeableto liquid. Such drapes typically have a thickness in the range of 25-50microns. For permeable materials, the permeability generally should below enough that a desired negative pressure may be maintained. The cover125 may comprise, for example, one or more of the following materials:polyurethane (PU), such as hydrophilic polyurethane; cellulosics;hydrophilic polyamides; polyvinyl alcohol; polyvinyl pyrrolidone;hydrophilic acrylics; silicones, such as hydrophilic siliconeelastomers; natural rubbers; polyisoprene; styrene butadiene rubber;chloroprene rubber; polybutadiene; nitrile rubber; butyl rubber;ethylene propylene rubber; ethylene propylene diene monomer;chlorosulfonated polyethylene; polysulfide rubber; ethylene vinylacetate (EVA); co-polyester; and polyether block polymide copolymers.Such materials are commercially available as, for example, Tegaderm®drape, commercially available from 3M Company, Minneapolis, Minnesota;polyurethane (PU) drape, commercially available from Avery DennisonCorporation, Pasadena, California; polyether block polyamide copolymer(PEBAX), for example, from Arkema S.A., Colombes, France; and Inspire2301 and Inpsire 2327 polyurethane films, commercially available fromExpopack Advanced Coatings, Wrexham, United Kingdom. In someembodiments, the cover 125 may comprise INSPIRE 2301 having an MVTR(upright cup technique) of 2600 g/m²/24 hours and a thickness of about30 microns.

An attachment device may be used to attach the cover 125 to anattachment surface, such as undamaged epidermis, a gasket, or anothercover. The attachment device may take many forms. For example, anattachment device may be a medically-acceptable, pressure-sensitiveadhesive configured to bond the cover 125 to epidermis around a tissuesite. In some embodiments, for example, some or all of the cover 125 maybe coated with an adhesive, such as an acrylic adhesive, which may havea coating weight of about 25-65 grams per square meter (g.s.m.). Thickeradhesives, or combinations of adhesives, may be applied in someembodiments to improve the seal and reduce leaks. Other exampleembodiments of an attachment device may include a double-sided tape,paste, hydrocolloid, hydrogel, silicone gel, or organogel.

The solution source 145 may also be representative of a container,canister, pouch, bag, or other storage component, which can provide asolution for instillation therapy. Compositions of solutions may varyaccording to a prescribed therapy, but examples of solutions that may besuitable for some prescriptions include hypochlorite-based solutions,silver nitrate (0.5%), sulfur-based solutions, biguanides, cationicsolutions, and isotonic solutions.

Therapy Modes

In operation, the tissue interface 120 may be placed within, over, on,or otherwise proximate to a tissue site. If the tissue site is a wound,for example, the tissue interface 120 may partially or completely fillthe wound, or it may be placed over the wound. The cover 125 may beplaced over the tissue interface 120 and sealed to an attachment surfacenear a tissue site. For example, the cover 125 may be sealed toundamaged epidermis peripheral to a tissue site. Thus, the dressing 110can provide a sealed therapeutic environment proximate to a tissue site,substantially isolated from the external environment. Thenegative-pressure source 105 and the solution source 145 can be fluidlycoupled to the tissue interface through one or more fluid conductors.The negative-pressure source 105 can reduce pressure in the sealedtherapeutic environment, and fluid from the solution source 145 can beinstilled to the sealed therapeutic environment.

The fluid mechanics of using a negative-pressure source to reducepressure in another component or location, such as within a sealedtherapeutic environment, can be mathematically complex. However, thebasic principles of fluid mechanics applicable to negative-pressuretherapy and instillation are generally well-known to those skilled inthe art, and the process of reducing pressure may be describedillustratively herein as “delivering,” “distributing,” or “generating”negative pressure, for example.

In general, exudate and other fluid flow toward lower pressure along afluid path. Thus, the term “downstream” typically implies something in afluid path relatively closer to a source of negative pressure or furtheraway from a source of positive pressure. Conversely, the term “upstream”implies something relatively further away from a source of negativepressure or closer to a source of positive pressure. Similarly, it maybe convenient to describe certain features in terms of fluid “inlet” or“outlet” in such a frame of reference. This orientation is generallypresumed for purposes of describing various features and componentsherein. However, the fluid path may also be reversed in someapplications, such as by substituting a positive-pressure source for anegative-pressure source, and this descriptive convention should not beconstrued as a limiting convention.

Negative pressure applied across the tissue site through the tissueinterface 120 in the sealed therapeutic environment can inducemacro-strain and micro-strain in the tissue site. Negative pressure canalso remove exudate and other fluid from a tissue site, which can becollected in container 115.

In some embodiments, the controller 130 may receive and process datafrom one or more sensors, such as the first sensor 135. The controller130 may also control the operation of one or more components of thetherapy system 100 to manage the pressure delivered to the tissueinterface 120. In some embodiments, controller 130 may include an inputfor receiving a desired target pressure and may be programmed forprocessing data relating to the setting and inputting of the targetpressure to be applied to the tissue interface 120. In some exampleembodiments, the target pressure may be a fixed pressure value set by anoperator as the target negative pressure desired for therapy at a tissuesite and then provided as input to the controller 130. The targetpressure may vary from tissue site to tissue site based on the type oftissue forming a tissue site, the type of injury or wound (if any), themedical condition of the patient, and the preference of the attendingphysician. After selecting a desired target pressure, the controller 130can operate the negative-pressure source 105 in one or more controlmodes based on the target pressure and may receive feedback from one ormore sensors to maintain the target pressure at the tissue interface120.

FIG. 2 is a graph illustrating additional details of an example controlmode that may be associated with some embodiments of the controller 130.In some embodiments, the controller 130 may have a continuous pressuremode, in which the negative-pressure source 105 is operated to provide aconstant target negative pressure, as indicated by line 205 and line210, for the duration of treatment or until manually deactivated.Additionally or alternatively, the controller may have an intermittentpressure mode, as illustrated in the example of FIG. 2 . In FIG. 2 , thex-axis represents time and the y-axis represents negative pressuregenerated by the negative-pressure source 105 over time. In the exampleof FIG. 2 , the controller 130 can operate the negative-pressure source105 to cycle between a target pressure and atmospheric pressure. Forexample, the target pressure may be set at a value of −125 mmHg, asindicated by line 205, for a specified period of time (e.g., 5 min),followed by a specified period of time (e.g., 2 min) of deactivation, asindicated by the gap between the solid lines 215 and 220. The cycle canbe repeated by activating the negative-pressure source 105, as indicatedby line 220, which can form a square wave pattern between the targetpressure and atmospheric pressure.

In some example embodiments, the increase in negative pressure fromambient pressure to the target pressure may not be instantaneous. Forexample, the negative-pressure source 105 and the dressing 110 may havean initial rise time, as indicated by the dashed line 225. The initialrise time may vary depending on the type of dressing and therapyequipment being used. For example, the initial rise time for one therapysystem may be in a range of about 20-30 mmHg/second and in a range ofabout 5-10 mmHg/second for another therapy system. If the therapy system100 is operating in an intermittent mode, the repeating rise time, asindicated by the solid line 220, may be a value substantially equal tothe initial rise time as indicated by the dashed line 225.

FIG. 3 is a graph illustrating additional details that may be associatedwith another example pressure control mode in some embodiments of thetherapy system 100. In FIG. 3 , the x-axis represents time and they-axis represents negative pressure generated by the negative-pressuresource 105. The target pressure in the example of FIG. 3 can vary withtime in a dynamic pressure mode. For example, the target pressure mayvary in the form of a triangular waveform, varying between a negativepressure of 50 and 135 mmHg with a rise time 305 set at a rate of +25mmHg/min. and a descent time 310 set at −25 mmHg/min. In otherembodiments of the therapy system 100, the triangular waveform may varybetween negative pressure of 25 and 135 mmHg with a rise time 305 set ata rate of +30 mmHg/min and a descent time 310 set at −30 mmHg/min.

In some embodiments, the controller 130 may control or determine avariable target pressure in a dynamic pressure mode, and the variabletarget pressure may vary between a maximum and minimum pressure valuethat may be set as an input prescribed by an operator as the range ofdesired negative pressure. The variable target pressure may also beprocessed and controlled by the controller 130, which can vary thetarget pressure according to a predetermined waveform, such as atriangular waveform, a sine waveform, or a saw-tooth waveform. In someembodiments, the waveform may be set by an operator as the predeterminedor time-varying negative pressure desired for therapy.

FIG. 4 is a chart illustrating details that may be associated with anexample method 400 of operating the therapy system 100 to providenegative-pressure treatment and instillation treatment to the tissueinterface 120. In some embodiments, the controller 130 may receive andprocess data, such as data related to instillation solution provided tothe tissue interface 120. Such data may include the type of instillationsolution prescribed by a clinician, the volume of fluid or solution tobe instilled to a tissue site (“fill volume”), and the amount of timeprescribed for leaving solution at a tissue site (“dwell time”) beforeapplying a negative pressure to the tissue site. The fill volume may be,for example, between 10 and 500 mL, and the dwell time may be betweenone second to 30 minutes. The controller 130 may also control theoperation of one or more components of the therapy system 100 to instillsolution, as indicated at 405. For example, the controller 130 maymanage fluid distributed from the solution source 145 to the tissueinterface 120. In some embodiments, fluid may be instilled to a tissuesite by applying a negative pressure from the negative-pressure source105 to reduce the pressure at the tissue site, drawing solution into thetissue interface 120, as indicated at 410. In some embodiments, solutionmay be instilled to a tissue site by applying a positive pressure fromthe positive-pressure source 150 to move solution from the solutionsource 145 to the tissue interface 120, as indicated at 415.Additionally or alternatively, the solution source 145 may be elevatedto a height sufficient to allow gravity to move solution into the tissueinterface 120, as indicated at 420.

The controller 130 may also control the fluid dynamics of instillationat 425 by providing a continuous flow of solution at 430 or anintermittent flow of solution at 435. Negative pressure may be appliedto provide either continuous flow or intermittent flow of solution at440. The application of negative pressure may be implemented to providea continuous pressure mode of operation at 445 to achieve a continuousflow rate of instillation solution through the tissue interface 120, orit may be implemented to provide a dynamic pressure mode of operation at450 to vary the flow rate of instillation solution through the tissueinterface 120. Alternatively, the application of negative pressure maybe implemented to provide an intermittent mode of operation at 455 toallow instillation solution to dwell at the tissue interface 120. In anintermittent mode, a specific fill volume and dwell time may be provideddepending, for example, on the type of tissue site being treated and thetype of dressing being utilized. After or during instillation ofsolution, negative-pressure treatment may be applied at 460. Thecontroller 130 may be utilized to select a mode of operation and theduration of the negative pressure treatment before commencing anotherinstillation cycle at 465 by instilling more solution at 405.

FIG. 5 is a graph illustrating additional details of another examplecontrol mode that may be associated with some embodiments of thecontroller 130 to provide negative-pressure treatment and instillationtreatment to the tissue interface 120. In the example of Figure thecontroller 130 is configured to provide discrete intervals of negativepressure and instillation. The controller 130 can operate thenegative-pressure source 105 in an intermittent-pressure mode tomaintain a target negative pressure 205 during negative-pressureintervals. During an instillation interval 505, the controller 130 candeactivate the negative-pressure source 105 and operate thepositive-pressure source 150 to instill a prescribed volume of fluidfrom the solution source 145 to a tissue site. The target negativepressure, the prescribed volume, or both, may be preset by thecontroller 130, or may be set by an operator at run-time in someexamples. The controller 130 may also provide a dwell interval 510,during which neither the negative-pressure source 105 nor thepositive-pressure source 150 is active. In some examples, the cycle canbe repeated. In the example of FIG. 5 , the controller 130 re-activatesthe negative-pressure source 105 after the dwell interval 510.

FIG. 5 further illustrates an example of the controller 130 configuredto provide intermittent purge cycles. In FIG. 5 , the controller 130periodically activates a first purge cycle 515 and a second purge cycle520. For example, the negative-pressure source 105 may be coupled to thedressing 110 through a first fluid conductor, and the controller 130 mayactivate the first purge cycle 515 by opening a valve to expose thefirst fluid conductor to ambient pressure or positive pressure. Thepressure increase can force exudate out of the first fluid conductor,reducing exudate build-up that can block the first fluid conductor.Similarly, the solution source 145 may be coupled to the dressing 110through a second fluid conductor, and the second purge cycle 520 maycomprise instilling a relatively small volume of fluid from the solutionsource 145 through the second fluid conductor. For example, a suitablepurge volume may be in a range of about 0.1 milliliters to about 1milliliter. The purge frequency may also vary. In some embodiments, thefrequency may be in a range of about 5 to 20 minutes. In someembodiments, a purge volume of about 0.2 milliliters and a frequency ofabout 10 minutes may be suitable for reducing material deposits in thesecond fluid conductor near the dressing 110. The second purge cycle 520can be activated during a negative-pressure interval, as in the exampleof FIG. 5 , or between negative-pressure intervals. The purge volume ofsolution may be removed by negative pressure through the first fluidconductor in some configurations. In some examples, the first purgecycle 515 and the second purge cycle 520 can be activated concurrently.

The systems, apparatuses, and methods described herein may providesignificant advantages. For example, interaction between instillationsolutions and proteins and lipids from exudate can produce stickydeposits that can collect at a dressing interface. Instillation purgecycles can substantially reduce or eliminate these deposits which canocclude fluid conductors and other distribution components.

While shown in a few illustrative embodiments, a person having ordinaryskill in the art will recognize that the systems, apparatuses, andmethods described herein are susceptible to various changes andmodifications that fall within the scope of the appended claims.Moreover, descriptions of various alternatives using terms such as “or”do not require mutual exclusivity unless clearly required by thecontext, and the indefinite articles “a” or “an” do not limit thesubject to a single instance unless clearly required by the context.Components may be also be combined or eliminated in variousconfigurations for purposes of sale, manufacture, assembly, or use. Forexample, in some configurations the dressing 110, the container 115, orboth may be eliminated or separated from other components formanufacture or sale. In other example configurations, the controller 130may also be manufactured, configured, assembled, or sold independentlyof other components.

The appended claims set forth novel and inventive aspects of the subjectmatter described above, but the claims may also encompass additionalsubject matter not specifically recited in detail. For example, certainfeatures, elements, or aspects may be omitted from the claims if notnecessary to distinguish the novel and inventive features from what isalready known to a person having ordinary skill in the art. Features,elements, and aspects described in the context of some embodiments mayalso be omitted, combined, or replaced by alternative features servingthe same, equivalent, or similar purpose without departing from thescope of the invention defined by the appended claims.

1.-11. (canceled)
 12. A method of treating a tissue site withnegative-pressure and therapeutic solution, the method comprising:delivering the negative pressure to the tissue site for a firstinterval; delivering a fill volume of the therapeutic solution to thetissue site for a second interval; and delivering a purge volume of thetherapeutic solution to the tissue site.
 13. The method of claim 12,wherein the purge volume is delivered during the first interval.
 14. Themethod of claim 12, wherein the purge volume is delivered before thefirst interval.
 15. The method of claim 12, wherein the fill volume isat least 10 times the purge volume.
 16. The method of claim 12, whereina ratio of the fill volume to the purge volume is in a range of about10:1 to about 5000:1.
 17. The method of claim 12, wherein the purgevolume is in a range of about 0.1 milliliters to about 1 milliliter. 18.The method of claim 12, wherein the purge volume is delivered at afrequency of no greater than 20 minutes.
 19. The method of claim 12,wherein the purge volume is delivered at a frequency of not less than 5minutes.
 20. The method of claim 12, wherein the purge volume isdelivered at a frequency between about 5 minutes and about 20 minutes.21.-30. (canceled)
 31. An apparatus for treating a tissue site, theapparatus comprising: a supply of negative pressure; a solution source;and a controller operatively coupled to the supply of negative pressureand to the solution source, the controller configured to: delivernegative pressure to the tissue site for a negative-pressure interval;deliver a fill volume of instillation fluid to the tissue site for aninstillation interval; and deliver a purge volume of instillation fluidto the tissue site at a purge frequency in response to completion of theinstillation interval.
 32. The apparatus of claim 31, wherein thecontroller is configured to deliver the purge volume of instillationfluid during the negative-pressure interval.
 33. The apparatus of claim31, wherein the fill volume is at least 10 times the purge volume ofinstillation fluid.
 34. The apparatus of claim 31, wherein a ratio ofthe fill volume to the purge volume of instillation fluid is in a rangeof about 10:1 to about 5000:1.
 35. The apparatus of claim 31, whereinthe fill volume is in a range of about 10 milliliters to about 500milliliters, and the purge volume of instillation fluid is in a range ofabout 0.1 milliliters to about 1 milliliter.
 36. The apparatus of claim31, wherein the purge frequency is in a range of about 5 minutes toabout 20 minutes.
 37. The apparatus of claim 31, wherein: the fillvolume is in a range of about 10 milliliters to about 500 milliliters;the purge volume of instillation fluid is in a range of about 0.1milliliters to about 1 milliliter; and the purge frequency is in a rangeof about 5 minutes to about 20 minutes.
 38. The apparatus of claim 31,further comprising a fluid conductor fluidly coupled to the solutionsource, and wherein the controller is configured to deliver the purgevolume of instillation fluid through the fluid conductor.
 39. Theapparatus of claim 31, further comprising a first fluid conductorfluidly coupled to the supply of negative pressure, a second fluidconductor fluidly coupled to the solution source, and wherein thecontroller is configured to deliver the purge volume of instillationfluid through the second fluid conductor and to remove the purge volumeof instillation fluid through the first fluid conductor.
 40. Theapparatus of claim 31, further comprising a user interface coupled tothe controller and operable to receive input to configure at least oneof the purge volume of instillation fluid and the purge frequency.